From: Axel Kohlmeyer (
Date: Wed Aug 27 2003 - 10:19:44 CDT

hello fred,

i have to support john's opinion. even if you would expect a better
performance from a dual-xeon machine, there is a high chance,
that you would not get it. i have recently done a series of benchmarks
on a selection of PC hardware (and some workstation machines) and have
found, that the SMP performance on dual-xeon machines is horrible for
any application that does not stay mostly in the cpu-cache (i.e. almost
any serious application). on top of that you should keep in mind, that
current PC hardware is so memory bandwidth starved, that you need
low-latency, dual-channel memory to unleash the full power of a single
CPU machine. you can look up some of my dual-cpu benchmark numbers at
so that you can see for yourself.

hope this helps,

>>> "JS" == John Stone <> writes:

JS> Dear Fred,
JS> I believe that the problems with SMP machines and NVidia boards
JS> have been fixed since I wrote that email. In the last year I can
JS> say that the NVidia SMP problem we used to see seem to have gone away.
JS> I tested the Wildcat 7100 series drivers back in April/May and at
JS> the time they did not support SMP kernels at all. I.e. the driver
JS> won't even load. This was a documented limitation with the Wildcat
JS> drivers I tested at the time. I suspect this is still the case, but
JS> to make sure, you should send an email to the 3DLabs folks. Also,
JS> the Wildcat Linux drivers are picky about what motherboards they support,
JS> I had to get a loaner machine to try out with the Linux drivers because
JS> none of our machines had the right motherboard chipset to work with the
JS> drivers I tested.

JS> Regarding CPUs, I personally favor Athlon-based systems as they
JS> perform better on the codes I tend to run. Your mileage will vary.
JS> The Wildcat Linux drivers don't support Athlon yet, so if you have
JS> an Athlon, your only option would be to go with NVidia or ATI.

JS> Of the 3 major vendors with Linux drivers, NVidia's drivers are
JS> the most mature and full-featured. ATI's are next maturity-wise,
JS> and the 3DLabs drivers are the youngest and have the most work
JS> ahead of them as far as stability and completeness goes.

JS> In the long run the 3DLabs hardware is definitely the way to go,
JS> as their cards perform faster than the others, at least with VMD,
JS> I can't give them much of a recommendation yet since I only got to run
JS> test drivers, and they don't support the Athlons I have in my office.
JS> If you're interested in the 3DLabs cards, I'd definitely suggest to get a
JS> "demo board" to try out with the Linux drivers before you commit to
JS> them since they weren't quite ready for running VMD last I checked.

JS> For what it might cost to purchase a Xeon based machine, you could
JS> probably afford to buy a real Unix box from Sun or SGI, with a good
JS> graphics board even, so I'd recommend against going with Xeons.

JS> I'm biased as I personally would MUCH rather use a stable machine like
JS> a Sun/SGI box than a PC for graphics work. So, unless you've got a good
JS> reason to blow cash on a Xeon, I'd stick with more cost-effective
JS> options or else just buy a real workstation.

JS> I hope that's somewhat useful information for you.

JS> Thanks,
JS> John Stone

JS> On Tue, Aug 26, 2003 at 08:49:41PM -0400, Fred Salsbury wrote:
>> Hello all --
>> I've been using VMD for a few years, but I am new to this list.
>> I am looking to acquire a workstation primarily to use with VMD and I was
>> looking through the archives of the mailing list, and I came across the
>> following remark by John Stone (in reply to someone mentioning wanting to
>> run on a dual Xenon workstation:
>> >>>>
>> Several of the vendors have had problems with their OpenGL drivers
>> on SMP machines, so any comments you have about the stability you get on
>> such machines would be very interesting.
>> >>>>
>> Can someone comment on this? I was pondering either one of the new dual
>> 3.06MHz (1MB L3 Cache) Xenon workstations or a P4 3.2GHz desktop, and with
>> either a Nvidia QuadroFX 1000 graphics card or a 3Dlabs Wildcat4 7110
>> graphics card. So I'm wondering if there have been noticeable stability
>> problems, and is an AMD athlon workstation would be better then.
>> thanks!
>> Fred
>> Dr. Fred Salsbury
>> Assistant Professor
>> Department of Physics
>> Wake Forest University

JS> --
JS> NIH Resource for Macromolecular Modeling and Bioinformatics
JS> Beckman Institute for Advanced Science and Technology
JS> University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
JS> Email: Phone: 217-244-3349
JS> WWW: Fax: 217-244-6078

Axel Kohlmeyer       e-mail:
Lehrstuhl fuer Theoretische Chemie          Phone: ++49 (0)234/32-26673
Ruhr-Universitaet Bochum - NC 03/53         Fax:   ++49 (0)234/32-14045
D-44780 Bochum         
If you make something idiot-proof, the universe creates a better idiot.